Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.
Memory devices are one type of semiconductor device. Memory devices typically include an array of memory cells, with each memory cell being adapted to store digital information or data as a “1” or “0”. Some memory devices are referred to as volatile memories because of their need to be refreshed to retain the data, while others are referred to as non-volatile memories (NVMs) because they do not require refreshing.
A recent development in NVMs is multiple-time programmable (MTP) NVMs, which are programmable multiple times. In comparison with high density NVM (such as flash memories or E2PROMS), MTP memories are suitable for low density applications, and are usually characterized by a larger memory cell size and a lower number of masking operations required to manufacture the memory cells.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.